Re: [gtk-list] Re: how to convert windows RGB color to GdkColor

[Tomi Ollila <Tomi Ollila tfi net>]

Tuesday Aug 31 22:44:24 -0600 1999 Joe Pfeiffer <pfeiffer@cs.nmsu.edu> wrote:
>    Right-shifting to convert from 16bpp to 8bpp works fine:
> 
> 	   0xFFFF (full-bright) becomes 0xFF (full-bright).
> 
>    But left-shifting doesn't:
> 
> 	   0xFF (full-bright) becomes 0xFF00 (less-than-full-bright).
> 
>    Adding in the old value is a fast way to scale the values properly, so 0xFF
>    becomes 0xFFFF.  You can multiply by 257.0 if you prefer :)
> 
> This is true of the special case of
> 1) old value was ff, and
> 2) you really meant full-bright, that didn't just happen to be what
> you got.
> 
> (and the analogous 0x00 case).  It doesn't follow in general, though.

Why it doesnt ? :


old color       new color
dec  hex        dec hex
 0   00          0   0000
 1   01         257  0101
 2   02         514  0202
...
63   3f        16191  3f3f
...
254  fe        65278  fefe
255  ff        65535  ffff

> 
>    Go Lobos!

> Joseph J. Pfeiffer, Jr., Ph.D.       Phone -- (505) 646-1605


Tomi